METAL MAST AND VERTICAL ANTENNA

[nitroturbo4u]

:thumbdown
Seen alot of info on this latelty.I see in theory how this will screw things up on a beam (yagi).
I guess the only way around this is to mount the "metal mast" behind the reflector.
Like a inverted L config.
Worried about my super scanners now...However the driven elements are above the mast.Maybe a 2 inch fiberglass rod or some other non-conductor with a high tensile strength.
Let me know what ya think.

Radio is the theater of the mind; television is the theater of the mindless :headbang

 

[Captain Kilowatt]

There is a small interaction with the mast but nothing to really worry about on 11m. Half the element length is always clear of the mast anyway. Smaller VHF and some UHF antennas are designed to be end mounted. I have a dual band antenna with 5 elements on 2m and 5 elements on 70 cm that is meant to be mounted at the end of the boom to avoid interaction with the mast. With a super scanner antenna the elements are not in the same plane as the mast like a yagi so interaction should be even less. Trying to use a non-conductive mast that long on something that size is going to lead to mechanical trouble due to strength issues and is not worth even attempting. Neither you nor your contacts will see any difference however after the next windstorm you may see a difference in what your antenna looks like after you go see it in your neighbor's yard.

 

[hookedon6]

if you are REALLY concerned, then use a fiberglass mastop:

damn,... CK beat my post by 1 minute

 

[W5LZ]

What do I think about it?
I think that in general, in most cases, it won't make enough difference to make any significant difference at all. Or, rather than 'significant', how about 'discernible' difference? In some extreme cases you might even notice something being slightly different, but don't hold your breath.
- 'Doc

 

[Shockwave]

If the conductive mast is effecting the antenna performance being inline with the elements, changing to a fiberglass mast is not likely to make a difference unless you use some new type of non conductive coax too. You'll still need to route the coax down the mast in most cases. Choking the coax may help it from radiating much energy but the fact the conductor is still right in the near field will cause most of the same pattern distortion. The good news is the effects are very small on this band and not worth worrying about unless you make the mistake of installing a 3 element vertical yagi.